sounds like he was a hell of a good man, the same way with this character with the flowbench here in south dakota, he says he doesnt want to give out all of his secrets, yet pretty much tells me everything he knows, which i really appreciate, but like i said i have to doubt some of it. I had him flow my first set of heads before i was in high school (14 i believe) and they turned out okay, he really never instructed me how to improve them since they were pretty close to his common run of the mill SBC production casting numbers but once we got going on this AMC stuff he really tried to help, what he said really didnt pay off as much as he thought, but it did help some, but according to him these heads are extremely difficult to work with, the ports are paper thin, and the shaping isnt the greatest

sorry to poke and bother bogie, but is that reply you were making extremely long, ???

Actually the respnse is fairly long but the real problem is that I'm in two different places with different computers at each location, the one I'm at doesn't have my response to you on it and I just haven't felt like repeating all I said from memory. When I get home I can finish up and get it too you.

Your porting guy is correct about the AMC head, it does have very thin walls which really restrict how much grinding you do. The intakes are rather abrupt on the short side turn into the pocket. However, the guides tend to be thick which allows some nice shaping to capture the flow and direct it around the spark plug side on the port. The chamber is too open which tends allow the swirl to self dampen, this is a problem with all open chambers. The spark plug is in a location where it tends to get wet from fuel which slows the initial flame kernel and its well off to the side so the burn is slower to propagate, just another trait of open chambers. The typical solution is to bump up the ignition timing both in amount and rate, but this tends to make the engine more detonation sensitive.

On the exhaust side, the short side turn comes off from the valve too abruptly, like a small block Chrysler. On top of this the side of the valve toward the combustion chamber is too open. (compare the chambers you have to those of a Vortec or Fastburn head, you'll see the shape you need. This allows too much flow form that side which then interfers with the flows developing from the center of the cylinder. The end result is that the port area appears too small to the flow. Short of cutting the exhaust ports off as done for the Ford 351Cleveland and 429/460 heads, there's not much you can do short of welding the port shut and starting over. that just isn't practicle with cast iron. It needs a higher exhaust port, but there isn't enough material to shape it properly without getting wet. These are very much SMOG heads and there just isn't a lot that can be done with them. The simple solution is to supercharge the engine since port shapes, at least intake, are less sensitive when there's higher than atmospheric pressure in them. Nitrous will wake this engine up but it is more dependent on port shape when the engine is normally asperated just like what you're into now.

I know that back in the late 60s and early 70s the Javalen had some modest road course success, but there's a reason whay they never caught on with the street crowd beyond the denim upholstery.

You said something about working on a Small Block Ford, even with emissions heads these are much more responsive than the AMC. Almost as good as the equivalent SBC.

One of the tricks I've found over the years that sometimes works is to widen the floor of the intake as it approaches the pocket. This slows the flow and sometimes helps it around the short side turn. But this begins to introduce a tumble flow on the inside of the cylinder, this will work against fuel economy, but may improve low valve opening flow.

These are things you have to expirement with, which is why I suggested making models rather than carving up 401 heads, there just can't be that many of them. You cast the stock ports and combustion chamber with RTV molding rubber available from larger hobby shops. Build a wooden box that can be dissassembled after casting a part. Line the box with pieces of polyproplene, IE plastic milk bottle or gas/water can material as resins won't stick to this stuff. Make sure all seams are sealed with some RTV. Fill the cavity with casting resin (urethane or styrene polyester will do) remove the casting from the mold when the stuff is cured. Remove the RTV of the ports and cc from the casting. Make a bunch. Then start modifing the shapes of the ports and test on them on the flow bench.  

Bogie

I realize that im adding to your work even more in trying to respond to my questions, but i was just looking at some Reher Morrison flow charts that i found on the net and figured that id better ask you about some of the numbers they used on them. I am familiar with figuring the discharge coefficient of the valve but really what can be seen from these numbers, and what can they be used for?i realize that the higher percentage the more efficient the valve is, but reher morrison used in conjunction with the actual flow area presented by the valve to get a "effective" flow area, this made me think about what you said about trying to discourage flow from the shrouded side of the valve because it creates a swirl reversal, so is it necessarily the higher the discharge coefficient of the valve the better? I am still very interested on what you do on the seats on the shrouded side of the valve to discourage flow, im racking my brain on what to do there on the shrouded side of the port for the jobs that i have here now (thank god im porting heads for friends and local racers for motors that will never see a dyno that i can "screw-up" and get some practice on and later on learn what i did "wrong" to improve my own heads, lol).

You may have answered this for me already but why does incorporating a tumble effect on the short side turn work against gas mileage? Im a devoted reader of a lot of Jim McFarland stuff and i get the idea that according to him that mixture motion is good in any way shape or form.

Just another thing that i figured id be interested in what you would have to say, in the July Popular Hot Rodding there is some tests done by David Vizard on some Dart Iron Eagle Big block heads, the heads had a horrible swirl reversal at the midrange lifts, one is getting too much flow on the shrouded side of the valve the common cause for this, and two Vizard said that a engine over 460 cubic inches the cylinder heads cant really get large enough for the displacement you have to fill no matter what, so the overly high intake port velocities "eat up" the poor swirl, were you referring to small block chevys onyl when you were talking to me about this earlier, or do you disagree with that statement

thanks for all your help bogie, and hopefully im not discouraging you from coming to the board because i have a endless amount of questions, haha

Gib, I'm going to get back to you but not tonight. Just a teaser though.

The reason Dave Vizard said what he did about 460 size engines (that is a Ford, isn't it?) is more specific to pushrod engines. It's the old square-cube law where the insides are growing to the cube of the exterior dimensions that only are growing to the square. What this means is that you run out of space to distance the pushrods apart( and to some extent the head bolts) faster than the displacement grows. Therefore you can't distance the pushrods enough to make a port sufficient large that that fits between them that will feed the displacement. Overhead cam engines have much less of a problem in this regard. Ford went to tunnel ports to work around the problem, but these caused other feeding woes.

I tell ya being an engineer is tough work, trying to find clever solutions to all these constraints.

Bogie 

I tell ya being an engineer is tough work, trying to find clever solutions to all these constraints.
I apologize for asking you to respond to what other people have said, but it really bothers me not to doubt everything i see, hopefully my next question you dont need to be in such a engineers frame of mind to answer. Im really searching for a way to get my hands on a sort of flowbench at the current time. I am looking very closely to Audie Quik Flow and am getting interested and would like to ask your opinion on it. If it is close enough to the real thing to waste $750 or so dollars on it or is it a better idea for me to put myself through college and then try just to get the real thing afterwards, thanks again, i promise this is my last question for a while!

This is a neet piece of equipment and is a great compliment to the flow bench that David Vizard shows how to build in his Chevy cylinder head book. You need the software unless your adept at the science of fluid dynamics and are comfortable with the Calculus.

You'll also need to fab necessary adapters for the flow bench, make a real good gadget to open and control the valves and a dial micrometer for accurate opening measurements. Of course you need all this stuff for the Vizard flow bench.

What the Audie Quick Flow does is that if you have a home made  or old flow bench it puts you into the computer based computational fluid flow game right away. If you have to build or acquire the basic flow bench, it may not save all that much money against the cost of a Superflow unit with the same bells and whistles.

Bogie

Even though im done asking questions for a while, i might as well still Bump this

Are you back at home yet bogie?

Back and have both lap tops with me.

Bogie

Great! I will be patiently awaiting some more of your insight!

Sorry to add to your workload even more on trying to answer  my previous questions but when you speak of swirl so highly in your previous posts, is the highest swirl possible a requirement for a "all-out" engine? could ultra high RPM's and compression ratios get the desired tubulence without the high swirl and then could you aim more efforts to achieving more flow, maybe more around the "more" of the valve. I'm aware this is currently somewhat of a controversy, that if you didn't have swirl more energy could be used for outright mass flow, but I'm unaware of any testing done in this regard. Could this be a path some of the aftermarket is currently taking, and could this be a reason that even small sized intake runner typically lose considerable low end torque to "factory" style heads. Like CHP's Impersonator and Impersonator II, considerable low end torque was lost and the only thing was changed was going from a 1.5-1.6 rockers and from vortec heas to AFR 180's. In theory I would think that the AFR heads would have a higher velocity (6.7% increase in flow (@.500) with only a 5.8% increase in volume) or at least close to the average port veocity of the vortec heads, so why such large loss of low end torque, does increasing rocker ratio a .100" decrease low end torque that much or there something involved in the cylinder heads hurting the low speed performance of this motor. One last quick question, does the Kamm style termination seem to adversly effect swirl in anyway, and does it effect fuel atomization enough to make a very noticeable different in low speed performance?

I tried to upload this the other day but it wouldn't take. So I filed it on my machine, then couldn't remember the exact file name as I have a bunch of files with similar names, but hunting by date I located it so hopefully here ya go.

All of this you have taught me sounds great for small block chevy and maybe something like a AMC (in regards to swirl at least), but now I'm dealing with the big block chevy's good/bad port configuration. I dug out my old car craft mag where Dave Vizard did some budget mods and porting to a set of open chamber oval port heads, but couldn't find anything on rectangular ports. In that article Vizard talks about biasing the "bad port" to try to direct flow to the center of the cylinder, but this contradicts his axiom about "letting the flow go where it wants to go", if the port is aimed for the cylinder wall side, why not let swirl direction go that way? Would this hurt flow significantly enough to require trying to direct more flow to the center of the cylinder and possibly producing less swirl?

The engine in question is going in a mud raccer. It is a mild 454 with only .550" lift and the owner has planned on a set of Canfield 305 cc rectangular port heads, how can I make these rectangular ports function as close to oval ports as possible? as I see that really a oval port would be a better choice, but that is out of my control. What you were talking of about widening the port on the short side interested me because fuel mileage is of no concern, and even though it would create a tumble I thought that the added low lift might help midrange torque, since it can be especially hard to recover from those shifts in mud.

Even though I doubt you've done this kind of racing before, if you have any info or theories on preparing a mud racing engine it would be greatly appreciated, there is loads of info on circle track and drag cars, but info on how things should be changed for off roading is hard to come by.

The big rectangular ports are comparable to the large oval ports, what works for the ovals will make a rectangle port happy. I see reading Mr. Vizard you cought him in some alternate thinking. All I can say is if you do this lstuff ong enough you'll see situations that cause you to rethink what you thought you knew, then you bounce back and forth a few times. This again goes back to what I said about art and science. If this was so well understood we would have a canned program for every engine/head/port combination that always guarranteed optimum results. But after 50 years of grinding on SBCs, 45 years on SBFs and 40 years on BBCs we still haven't found the ultimate port. So one can conclude that there's plenty of space to rethink the situation.

What David ment by good ports and bad ports on the BBC is related mostly to how the ports are fed by a single 2 or four barreled carburetor or a TBI injection. If you cartoon the carburetor and port layout of a head thats layed out with an I,E;I,E;I,E;I,E configuration and take into account all I've said of how inertia causes the flow to favor the outside of turns; then you can see that the first intake has the flow being set up right where you want it for maximum swirl on the port wall adjacent to the cylinder wall. The second cylinder back has some of this favor but the manifold is pretty close to straight, neutralizing flow favor, still OK as the port will do it's thing with this set up. A similar thing can be said for the third cylinder, but the flow is beginning to favor the port wall adjacent to the center of the cylinder, not what you want for swirl, your starting to loose some energy. The fourth cylinder is fed all wrong, here inertial fources in the mixture are pushing the flow toward the center of the cylinder which greatly impedes swirl. The SBC and SBF, BBF, SBChr, BBChr and many others also suffer this defficiency to some extent. The BBC, BBF and non Hemi BBChr do so to a larger degree because of the larger distances and sharper angles from throttle plate to valve. Remember what I said along time back about my first set of FE heads, how FoMoCo's engineers put a funny hump in the port, which I made straight. Upon firing the engine, you could instantly tell by sound that it had no power. That funny hump was put there by the factory to put the inertia caused wrong side flow back onto the cylinder wall side of the port, enhancing swirl. Taking that hump out removed maybe as much as a 100 horsepower and made the engine a complete dog under 4000 RPM.

Head design if not engine design from Detriot is one of those things that really gripes me. It seems for every good idea they come up with there's a bunch of bad ideas that get stirred into the mix of an engine's design. The SBC Mirror Port head works to maximize swirl for NASCAR engines, it is unique in the SBC family. It's layout compared to the standard SBC is I,E;I,E;E,I;E,I instead of E,I;I,E;E,I;I,E. Again, if you cartoon this for a center mount carb as required by NASCAR rules you see that flow inertia in every case is naturally maximized with out having to add energy robbing bumps or humps to correct flow errors. Add that to the SBC' terrific exhaust port exit angle and you've got one fantastic head. The only other people of all the domestic manufacturers that ever got this idea was Oldsmobile. But then they took a great intake and put on a head with crappy combustion chamber design and a lousy exhaust port. I could just choke those designers, I get so frustrated with this almost but never quite right stuff.

I'll go further in this vein and pick on Ford a bit which should go over well in a pro-Chevy column. Take the Windsor SBF 221-351, not a trashy power plant by anybody's standard. Put a set of tunnel port or Boss heads on it and go racing. Good results, reliable, pretty powerful, but OK the integration of the tunnel ports and the Boss heads needed to have some problems worked out. The solution, throw everything you learned on the Windsor in the trash and come out with a new 351. Enter the Cleveland, how this piece of crap ever developed the "performace" aura it did is way beyond me. Yes they solved the intake efficiency problem, great job, no arguments. BUT!!!!!!!, in the process they screwed up the exhaust port contour (we've been through this), incoproated the Oldsmobile rocker concept ( an idea that didn't work worth a hill-of-beans for Oldsmobile), completley changed the coolant return routing into a heavy complicated system that never could be made water tight, screwed up the lubrication susyem so bad that to race the engine you have to completely redo it with a soluting that requires external lines all over the place. I never came up against a stock Cleveland that if I could force him to hang out at red line for a couple, three miles the bottom end wouldn't come out. Dumb, dumb and dumber design work, but typical not just at Ford but everybody does it somewhere, sometime as well.

OK calming down, getting off my soap box, after all modern port fuel injection gets around most of these port flow alignment issues, the sun's out the grass is green, things are fine, nothing can go wrong.

Don't go nuts with what I said about converting the SBC or BBC to tumble port flow unless your building an engine that runs all the time above 6000 RPM, in fact think more like 7, 8, 9, 10 thousand RPM as a pretty steady diet. Don't kill the swirl in any 2 valve wedge engine you expect to get torque out of. This is strickly the zone of ultra high RPM professional drag engines. This isn't even done on a NASCAR engine, hence Mirror Ports, they engender high swirl at 5500, to maybe sprints into 8 or 9 thousand revs, certainly these engines run pretty steadily in the upper 6s to lower 7s of thousands of RPMs.

For your Mudder engine I'd hang with mostly cleaning up the ports, doing a good pocket. Do a 5 angle seat, maybe 30 degree intakes. You can always go back as everybody learns the engine and carve out more if it needs the top end.

Bogie  

After reading some of your responses, my partner in crime for head porting (don't worry, just my dad) wanted to ask you about a certain porting myth from long ago, which I believe is awfully strange but he thought was worth the time to ask. What have you heard about cutting a 60* cut into a 30* cut and locating the middle of the 45* (on the valve) on a sharp line between the two cuts. Wouldn't this possibly dig a "line" into the valve or would the seat material be softer than the valve and "pound in" first? Does this configuration have any performance value at all?

I will probably take your advice for the heads, and not overdo it,but what is your BBC "baseline" for a 5 angle valve job? also what kind of performance value do you really see from a 30* intake seat, I realize that it would improve the flow at .1,.2, and possibly .3, but didn't you state earlier that only certain heads with tight turns into the pocket prefer 30* seats and they especially work over .500 lift. Does the BBC have this "tight turn" you are talking about? Especially a aftermarket cylinder head, that possibly could've already worked out this problem.